[Pixel Dash]

I got in a wall and fell until the game wasn't pixelated

This is a Dreams-specific bug that has plagued many creations: coins picked up too quickly in succession don't add up to your score correctly; those coins get skipped over.

Coins don't count towards your score if you pick them up while you are still recovering from damage taken.

You can dash through walls if you use + after a mushroom jump. Need to be timed with direction input for great distance and big speed.

Pressing as you jump on top of an enemy rockets you upwards considerably (needs to be timed correctly).

If you press repeatedly quickly enough, you can jump up to four times before hitting the ground.

Fix the wall.

I'm not certain, but jumping while hitting a boost might launch you forward more than if you were on the ground. At least, that's what happened in Chillboarders, (in which Dennis-nine-five found out about it).
Here, the boost is too short to tell.

The game still often times deactivates my sprint. It can happen after eliminating an enemy, wall jumping, or boosting.

After hitting jump pad and dashed I went through wall and got stuck

The wall on the left at the start of the tutorial is not collidable, so you can fall off the map.